Many conventional circuits need a high order (greater than one) high-pass filter with a sharp band pass characteristic. Conventional approaches for implementing high-pass filters tend to use a passive approach or an active approach. Conventional active approaches use a number of transistors (i.e., 4 or more active transistors for a differential implementation, 2 or more transistors for a single ended implementation) to implement a second order filter. By implementing a number of active transistors, the overall die area of such an implementation is often substantial. For certain designs, such as preamplifiers in drive systems, integrated circuit real estate needs to be kept to a minimum.
It would be desirable to implement a second order high-pass filter with cross-coupled feedback for implementing Q enhancement.